High-Altitude Long-Range Airship Dynamic Model And Trajectory Optimiziation

Presently,there is a strong interest in developing high-altitude long-range airships. High-altitude long-range airships have wide applications in the fields of transportation, observation, and telecommunication services, etc. This dissertation researches some questions about dynamic model and trajectory optimization of high-altitude long-range airship.As the basis for the design of trajectory optimization strategies, this dissertation developed a mathematical model for the airship. Based on the physical principles of the airship operation, a nonlinear model is presented as the six-degree-of-freedom dynamic equation of motion.The airship is modeled with six dimensional nonlinear and coupled equations of motion .Particularly,the added mass force,air force and buoyancy was studied and three computing models were presented. And the three-degree-of-freedom dynamic equation of motion is also presented.Trajectory optimal model of the simplified motion was presented. The analytical solution for this optimal problem is studied. Path constraints are imposed on airship states and controls in obtaining optimal flight trajectories. Approximate analytical solutions of path are obtained under several simplifying assumptions. Then the velocity can be determined using maximum value principle.Direct collocation is used to get the numeric solution of the optimization of airship. This method uses a piecewise polynomial representation for the state and control variables, thus converting the optimal control problem into a parameter optimization problem. This parameter optimization is then solved by the method of SQP.Then airship optimal flight trajectories in the condition of different Performance indexes are computed by using the numerical and analytical solutions of optimal problem. And the results are discussed.